Self charging air-oil shock absorber



June 30, 1959 H. HARTEL SELF CHARGING AIR-on. SHOCK ABsoRBER Filed March 8, 1955 aina). ...s

A r Ton/ver United States Harel; Clevelandgohib; assigner te' cleveland Pneumatic' Industries,`-V Irre.; a` corporation 1Aof 'Ohio AppueafionqMarch s;a1955,;senaiisrmaz,83o.

Tclaimsr (cn zeri-64).?

invention"relates' to"wheel'fshocl*absorbers and m'orepar'ti'cularly j'toli'a. self-'charging' air-'oil 'shock' 'absoi-ber? It is` an important object of thisinventionlto provide ya 'shock absorber* mechanism" which automatically Y replenishes the'uid iniatslickabsorber to "replace any lost'byleakage. i

Itis"ano'therobject of this 'invention 'to provide a shock absorberwhich automatically maintains the static position ofthe' shock absorber at' the desired level;

It` is^`still;'another object of this invention to provide a 'shock'absorber 'and'spn'ng combination wherein means are provided to increase Atheload stroke efiiciency` when theimpact' velocity .absorbedj'by the device increases.

It'is still another 'object'ofthis "invention .to provide aman-#oilL shock "absorber having meansjto automatically pumpthe `oil fro'mthe reservoir to' the main shock ab-v sorber'chamber to replenishanyloss ofoil due tOleakage or the like.v

Further "objects 'andadvantages `willl appear frm `the followingldesc'ription and drawings; wherein:

Figure'lis'a longitudinal'section of the shock absorber according to this invention inits 'extended position;

Figure 2 is a fragmentary longitudinal section vofthe shock absorber Vshownin VFigure l showingthe position off the "elements when the .shock absorber is in 'its static position; and,`

Figure is a fragmentarylongitudinal'section showing the position' of the "shock "absorberl elements .'wh'en the unit is in 'its compressed'jposition.

In the preferred form of vthis invention' the` shock absorbe'rfis provided with" a'tubularcasing 10 'and a telescoping pluriger tubegll '.each provided with'a mounting p ortiorrs adapted to be :connectedVr tothe vvehicle :structureI Mounted 'on theupper end of the 'casing-10 is a gl'in'd'V nut. 12 i provided with seals 13"'and' 14 'engaging the walls of theplunger tube 11 and casing .10 respectively and preventing leakage therebetween. Threaded to the lwer 'end`lof"the 'plunger tube '11 is a piston head`l6 Whic'his providedwith` twoor 'more damping orifices 17 andfan inwardly extendinggend ange.18"againstr which ailatingjcylinderf19` seats when the shock absorber is in v1`ts'extended position. Aseal 21`carried bythe oatingycylinder '19.prevents' leakage between'the inner surface ofthe plunger Vtube 11:and the ilt'iating,cylinder.19.` Theiioatingylinder 19"in-,cooperation with the plunger tl1`l3``1'1`-dees`a high pressure chamber 22 which is isolat'e'dfrorn the rest ofthe shock absorber fluid'cavity.

A stem-member 23'is formed withla'threaded 'portion 24 'extendingthroughthe end of the Yfloating cylinder 19 and is 'provided'with a nut'fastener 26 which securely mounts the stern member on the iloating cylinder.- A seal 27 prevents leakage past Vthe'threaded portion 24. Thread# ed` to the lower end of thestern member-23 `is a plunger member 28'provided'with` a'flnge and skirt portion 29, whichextends radially, outinto` engagement with a cylin-` dii'c'aI'p'ortin 31 lformedon the floating cylinder19l The' n'g'e and "skirt portion 29 is" providdiwitl -two or more" 2 orifices. '.32 'which provide fluid communication the1pl'unger member 28to thein't'erio'r of'thefioating. cylinder 19. Positioned around the stem'merrib'er'tfisI a oating. piston `33 which is provided' with .seals1134i`and' 36' which'engage the st'em`rnenib`er 23`andf cylindfcall portion 31 respectively, j. dividing. thef` zonel w'thfir',

'7i and cylindrical portion 3'1 into a..pre`ssu re `.chmbi a liquid chamberSSL Thiliquidchamberl. isf fico" rnun'icaton' with tliel'ower' side `of -the`pllngermem 23 through the orifces32. y e c Mounted within the casinglUisa blkheadgfpro: vided' with.V a seal.V 41 engagiingfthe` innerrwall `'off thecasing lllanda.radial flange 42held` against a sl ei'43 formed `in thecasingfbyK angend'membeiQ 421' .lwhic .is threaded'into the end "of 'thecasing 1'0'` The ``g`lii`r1tf1ll1f 12., casing 10', bulkheadll." and flatinglcyliderfll!"co: operate'. to -form. a liquid 'chamberi 46 `-infconimil v ,tin: witlthe chamber 38'through` theoriiicesflillf Anteil reservoir 47`is defined' bythe bulkhead.39Q11d 'the 4end member 44.` V.l`he bulkhead 39'is formed `:vvitli'fan' extending bore 48-which projects through .fan-axially: exi tending,portionV 49 andlforms the(cylinderVV of-therinech; anisrr'rused to pump oilfrom the reservoir ,47totlie chamber '46. A stem seatmember ,51".is' .threaddlinto 'the'dower `end1of the axially' 'extending ypor`ti'0i1'f49,fand is provided with va central.extending .passage y52I terrn-inat ing atV its'upper end in a valve seatl SSand` abit'sQlwer end in the reservoir 47. A-iluid. seal 5l"'pre`vent`s;.leali-y age between the portion 49`fand'th'e stem seat member 51; Threaded 'on the lower end'lof' anaxialprojectinj on. the plunger member ZSis` la.cylindrical.piston,157 formed with an inwardly extending'aend'ange 'SSagainst Whicha check Valve 59 seats.: Aspring 61extends4be tween the check valve 59i'and .the projectionSG'and urges the check'valve into engagement..witlithe flange 58.' The ange 58 "defines a centrale .openingg62twhicl'1 issuiicientlyv large to receive fthe'..upper end` 'offthe stem seat member 51 withclearance as .bes't. seen.. in FigureZ and a fluid -seal .63 prevent'sffleakage between the walls of thebore-48and .thepis'ton-Sllv A'fcheck valve 69 iis positionedto normally seat against tlieupper end"of`an. axially extending-passage 71 formedinsthe projection 56 and prevent reversedflowffrom,thefchanr ber -46through passage 72and passage,71`,towardl`.the check Valve 59. 4 A spring 73f'eXtends between-thestem member 231 and the checlcvalve .69',and yresiliently;urges the latter againstV its seat.. Fill'fplugs ,7"6Q-are fused, to, Ytill the chambers YAi'andJ 46 and .the reservoir, 47 with` foil. Askirt member 64 is mountedlon. the, plunger tube 11 `by a :Snapl v ring Y66 Wandis adaptedfto.receive `the :upper end of ,the casing `10 .and .prevent dirt from. enteringinto the area above the glandnut 12;` Chargingiittings 67 arealso provided 'in the plungertubell .anclathefiioatf-z ing cylinder 19 tofpermit. thecliarginggof.thechambers 22'andf37 with a gas .underpressure.`

In vehicles of. the typecontemplated for1-installation` ofa shock .absorber and.`- spring according to this.-inv,en I tion, shock impacts :are normally in` the'- categoryfwhiclr produce AaY `relatively, .low :velocity in the rshock/ absorben mechanism.'V` However, on occasion; large" impacts, .-occur. due Yto unsually flange bumps .and the likeUwhichepgrodue highvelocity vin the shock absorber mechanisms; Thisshock absorber. fullyrmeets the problems .-presentedgibyt these various types .of shock-impacts lby providingainhigh; resistance tofmovement v when the.impact is. relatively.` large and lower resistance yto Imovement,-whemthe shock; impact issmallenzthus producing a soft-.actionewhenfsuch; action--is practicalv and. a harder actioni whenever necesal sary.. Also:thezpumpingr mechanism functionssduring: slow impact .to` replenishlany- -oil .whichE leaks -iromg-Qthea.v chamber 46pastrthe seals.1i3and.:63..vr D Iiriugithe:` as-t. sembly ofthe shock absorber, the chamber 37 is charged with pressurized gas at a low pressure and the chamber 22 is charged with pressurized gas at a higher pressure. Also the chambers 46 and 38 are completely filled with oil, the various volumes and pressures being arranged so that when the plunger tube 11 moves downwardly rela- -tive to the casing to the static position shown in Figure 2, oil flows from the chamber 46 through the orifices 32 into the chamber 38 thereby moving the floating piston 33upward1y along the stem member 23 compressing the ygas within the chamber 37 to the same pressure as the gas within the chamber 22. At this time the pressures within the chambers 22, 37, 38 and 46 are all substantially equal.

When the various elements are in the position shown in Figure 2, the oil within the bore 48 and in the passage 71 is isolated from the reservoir 47 by the seating of the check valve 59 on the seat 53. If there is insuicient oil within the chambers 46 and 38 'at this time due to leakage past the seals further downward movement of the plunger tube 11 relative to the casing 10 will cause the piston 57 to compress the liquid within the bore 48 and passage 71 and pump it up through the passage 71 past the check valve 69 into the chamber 46 thereby replacing the lost oil.

If the chambers 46 and 38 contain sufcient oil to compress the gas within the chamber 37 to substantially the same pressure as the gas within the chamber 22 when the elements assume the static position shown in Figure 2, the pumping mechanism will not function to transfer oil from the reservoir 47 to the chamber 46. This is due to the fact that as soon as the pressure in the chamber 37 is the same as the pressure within the chamber 22, the effective area of the oil operating on the floating cylinder 19 is increased by an amount equal to the area of the oating piston 33 so that it approaches the eiective area of the gas within the chamber 22 acting on the floating cylinder 19. Therefore, further motion of the plunger tube 11 downwardly relative to the casing 10 beyond the static position increases the pressure of the oil within the chamber 46 to a pressure higher than the gas pressure in the chamber 22 and causes the oating cylinder to move upwardly relative to the plunger tube 11 and casing 10 as shown in Figure 3. This can continue until the floating cylinder 19 abuts against a shoulder 80 formed in the plunger ltube 11 which limits upward travel of the iloating cylinder 19. lt is, therefore, apparent that the pumping mechanism only functions to replace the liquid -in the shock absorber which has leaked past the seals and that the pumping mechanism automatically becomes inoperative when the proper amount of liquid is present in the shock absorber.

When the shock absorber is absorbing low velocity impacts, the oil flows from the chamber 46 through the oriiices 32 into the chamber 38 with a suicient velocity to maintain the pressure within the chamber 38 substantially the same as the pressure within the chamber 46. Therefore, the initial portions of the stroke result in a compression of the gas within the chamber 37. Since the pressure within the chamber 37 is relatively low when the shock absorber is in the extended position, the gas absorbs only a relatively small amount of energy during the initial portions of the stroke. However, when the impact absorbed by the shock absorber is large resulting in a high velocity of movement of the plunger tube 11 relative to the casing 10, the orice 32 acts as a throttle which prevents the pressure within the chamber 38 from building up to the same rate as the pressure within the chamber 46. If the velocity of the plunger tube 1I is great enough, the pressure within the chamber 46 builds up -to a pressure higher than the pressure within the chamber 22 before the pressures within the chambers 38 and 37 reach the pressure of the chamber 22. Therefore, the effective area of the oil within the chamber 46 acting on the fioating cylinder 19 approaches the effective area of the gas in the chamber 22 on the oating cylinder 19 before the elements assume the static position and result in a movement of the floating cylinder 19 upwardly relative to the plunger tube 11 and casing 10 early in the stroke. Such movement of the floating `cylinder 19 relative to the plunger tube 11 results in compressing the gas within the chamber 22 in early portions of the stroke; and since the pressure within the chamber 22 is greater than the pressure within the chamber 37, a high resistance to motion of the plunger tube results. Of course, the pumping mechanism will not function on high velocity impacts due to the fact that the floating cylinder 19 moves upwardly relative to the plunger tube 11 before the static position of the elements is reached. Of course, the ow of oil through the orifices 17 to and from the zone above the piston head 16 absorbs energy in both types of operation.

It should be noted that overloading of this shock absorber is virtually impossible since there is always a column of compressible gas to cushion the impact thus preventing excessive pressures which would be possible if only liquids were used.

Those skilled in the art will recognize that the disclosed structure provides automatic means which are simple and essentially fool-proof for replacing the liquid which tends to leak through the seals of shock absorber units so that the proper amount of liquid is maintained within the shock absorber. Also means are provided which automatically adjust the resistance developed by the shock absorber to needs presented by a variety of shock loading.

Although a preferred embodiment of this invention is illustrated, it will be realized that various modifications of the structural details may be made without departing from the mode of operation and the essence of the invention. Therefore, except insofar as they are claimed in the appended claims, structural details may be varied widely without modifying the mode of operation. Accordingly, the appended claims and not the aforesaid detailed description are determinative of the scope of the invention.

I claim:

1. A shock absorber comprising first and second telescoping members cooperating to define a uid cavity, a floating element movable relative to said members carried by said first member separating a chamber from the remaining portions of said cavity, said chamber being charged with gas under pressure, one part of said remaining portions being filled with liquid and the other parts thereof wtih gas, a liquid reservoir in one of said members, and pumping means between said reservoir and said one part connected to said floating element, vsaid pumping means -being actuated by relative movement between said oating element and one member beyond a predetermined relative position for pumping liquid from said reservoir to said one part.

2. A shock absorber comprising iir'st and second telescoping members cooperating to define a nid cavity, a iioating element movable relative to said members carried by said rst member separating a chamber from the remaining portions of said cavity, said chamber being charged with gas under pressure, one part of said remaining portions being filled with liquid and the other parts thereof with gas, a movable pressure responsiver element separating said liquid and gas in said remaining portions, a liquid reservoir in one of said members, and pumping means between said reservoir and said one part connected to said floating element, said pumping means being actuated by relative movement between said float-ing element and one member beyond a predetermined relative position for pumping liquid from said reservoir to said one part.

3. A shock absorber comprising first and second relatively movable telescoping members cooperating to dene a fluid cavity, a floating element carried by said first member, separating a chamber from the remaining portion of said cavity, said chamber being charged with gas under pressure, one part of said remaining portions being filled reservoir in one of said members, pumping means between said reservoir and said one part connected to said floating element, said pumping means being actuated by said relative movement for pumping liquid from said reservoir to said one part, and means automatically rendering said pumping means inoperative when the velocity of said relative movement is above a predetermined value.

4. A shock absorber comprising first and second telescoping members, a fioating element movable relative to said members carried by said first member and cooperating therewith to define a first chamber charged with gas under pressure, said floating element providing a cylinder isolated from said first chamber, a fioating piston dividing said cylinder into second and third chambers, said second chamber being charged with gas at a pressure less than the pressure in said first chamber, said telescoping members defining a fourth chamber filled with liquid and connected to said third chamber, a reservoir containing liquid, pumping means connected between said oating element and said second telescoping member cooperating to pump liquid from said reservoir to said fourth chamber upon relative movement between said floating element and second telescoping member beyond a predetermined relative position.

5. A shock absorber comprising first and second telescoping members, a fioating element movable relative to said members carried by said first member and cooperating therewith to define a first chamber charged with gas under pressure, said floating element providing a cylinder isolated from said first chamber, a fioating piston dividing said cylinder into second and third chambers, said second chamber being charged with gas at a pressure less than the pressure in said first chamber, said telescoping members defining a fourth chamber filled with liquid and connected to said third chamber by fiow restriction means, a reservoir containing liquid, a cylinder and a piston, one carried by said floating element and the other by said second telescoping member and includes valve means cooperating to pump liquid from said reservoir to said fourth chamber upon relative movement between said floating element and second telescoping member beyond a predetermined relative position.

6. A shock absorber comprising first and second telescoping members, a floating element movable relative to said members carried by said first member and cooperating therewith to define a first chamber charged with gas under pressure, said floating element providing a cylinder isolated from said first chamber, a fioating piston dividing said cylinder into second and third chambers, said second chamber being charged with gas at a pressure less than the pressure in said first chamber and said third chamber being filled with liquid, said telescoping members defining a fourth chamber filled with liquid and connected to said third chamber by fiow restriction means, a reservoir containing liquid, and pumping means including an actuating member carried by said floating element for pumping liquid from said reservoir to said fourth chamber in response to relative motion between said floating element and said second member when said fourth chamber contains less than a predetermined amount of liquid.

7. A shock absorbing mechanism comprising a pair of relatively movable telescoping members, a variable volume chamber within said members completely filled with liquid, a liquid reservoir, a pump actuated by said relative movement connecting said chamber and reservoir operating to pump liquid from said reservoir into said chamber, first means associated with said pump sensing the volume of liquid contained in said chamber rendering said pump inoperative when said chamber contains more than a predetermined volume of liquid, and second means associated with said pump sensing the relative velocity between said members rendering said pump inoperative when the velocity of relative movement between said members is above a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 1,179,253 Westinghouse Apr. 11, 1916 1,291,016 Kellogg Jan. 14, 1919 2,389,849 Gruss Nov. 27, 1945 2,436,573 Heynes Feb. 24, 1948 2,724,590 Irwin Nov. 22, 1955 FOREIGN PATENTS 914,337 France June 17, 1946 

